Vacuum-tube system



Dec. 3, 1929. F. A. KoLsTER 1,738,495

n VACUUM TUBE SYSTEM Original Filed Oct. 21, 1925 Patented Dec. 3, 1929 UNITED STATES PATENT OFI-Ica lliMmERIM d. HOLSTER, 0F PALO ALTO, CALFORNIA, ASSIGNOB T0 FEDERAL TELE- GRAPE OMPANY, 0F Mmmm application tiled Uctober all, 1925, Serial No." 63,961.

` rent supply arrangement which under certitl tain subsisting conditions is more simple and, on the whole, more satisfactory than what has heretofore been available.

lin the past it has been the common practice to provide as a filament current source a low voltage storage battery, and in" addition, a high voltage battery or other high voltage source for the plate supply. Alternatively, the filaments and plates of vacuum tubes have been supplied with current from separate power sources (other than batteries) each fed by alternating current and each c0mpris-l ing one or more rectiers, together with a filter networlr-which, in the aggregate, is quite expensive Still another expedient is to resort to the use of alternating current tubes in which the cathodes are operated on low voltage'alternating current without the use of rectifiers and fllters-thus avoiding the need of a storage battery or the alternative lament current rectifier and filter, `which are costly items. But alternating current tubes are comparatively expensive and, moreover, are not well adapted for certain lrinds of service, as for instance, airplane communication. On the other hand, storage'batteries are highly objectionable, if not entirely impracticable, for airplane service, and they are quite'undesirable for'use with broadcast receivers.. It is, nevertheless, apparent that the ordinary inexpensive direct current three electrode tube has some distinct inherent advantages, economically and otherwise, providing a more satisfactory power supply equipment canbe hadthan has been available in the past. lduch an equipment is provided by the present invention.

SAN' FRANCISCO, CALIFORNIA, A CORPGRALTIN Uli CM1'- "VACUUIMI-T'UBE SYSTEM Renewed @ctober 30, lett.

'llhe invention consists in providing in conu junction with a vacuum tube receiving sys tem a high frequency oscillator-preferably a vacuum tube oscillator-adjusted to operate at a frequency above audibility andarranged to supply super-audible high frequency current to both the filament and plate circuits of the receiving tubes. 'lhe current supply being of a frequency above good audibil ity, does not of itself produce an objectionable audible tone.

lll/here it is desirable to receive by the heterodyne or super-heterodyne method, the local frequency may be selected accordingly, either to produce an audible or an inaudible beat frequency wave by combining with the incoming wave.

A preferred embodiment of this invention will be described in detail with reference to the accompanying drawing.

lln the drawings:

' Figure l of the drawing shows the complete circuit with the frequency changer or oscillator being energized from a source of alternating current of standard frequency.

Figure 2 is a modification of thc-system shown in liig. 1 in which the frequency changer or oscillator is inductively coupled to the tube circuits. Y

t lln the past, it has been the practice to energize the output circuitsof vacuum tubes or electron-emission tubes with a source of direct current such as a battery or a rectifier energized from alternating current.. With the system of this invention, a pulsating or periodically varying current is empio ed. ln order t0 make these variations inaudible,

the frequency 'is made inaudible or above 10,000 cycles per second. 'lhe .system may` be employed with an alternatlng current source ofV audible frequency by employlng a frequency changer which will convert the low frequency current to one of relatively high frequency without audible ripples or modula tions.

In the drawings the system has been shown applied to two tubesl0 and 1l,respecti vely, altho it is to be understood that it 1s equally applicable to a single tube. These two tubes `are each provided with input or controlling circuits and output circuits, tube 10 having an input circuit 12 and an output circuit 14 and tube llhaving an input circuit 13 and output circuit 15. These tubes are preferably of the standard three element type each comprising a' grid or control element 16, a plate 17 and an electron-emission element or filament 18. The input circuit 12 of the tube 10 preferably comprises an inductance 19, one end of which is connected to the grid 16 and the other ,end of which is connected to one filament terminal at 20. The inductance 19 is coupled electrically with a source of modulated carrier wave signals such as an antenna 21, connected Vto the primary inductance 22 which is inductively'coupled to the inductance 19. The lower end of the primary inductance-22 is connected to ground 23 in the usual manner. The input circuit may be further provided with a C-battery 24 for plac- 'ing a negative potential on the grid 16. The amount of negative potential placed upon the grid 16 will determine whether the tube 10 will function as anamplifier or a modulator.

The output circuit of the tube 10 preferably comprises an inductance 25 one end of which is connected to the plate 17 and the other end of which is connected to the frequency changer or oscillator later to be described. This inductance 25 is preferably inductively coupled with the inductance 26 of the input circuit 14 of the detector tube 11. Input circuit 14 also preferably comprises a grid condenser 27 which is connected in series between the grid 16 and one end of the inductance 26. This 4grid condenser is provided with the usual leak 28. The output circuit 1 5 of the tube 11 preferably comprises an inductance 29, one end of which is connected to the plate 17, the other end being connected tothe oscillator as presently described. Inductance 30 is inductively coupled with the inductance 29 and suppliesthe lines 31 and 32 with the output current for the entire system. Means have also been provided for -tuningithe input circuits of the tubes 10 andr 11,and for this purpose there is preferably provided a variable condenser 33 which is shunted across the inductance 19 and a variable condenser 34 which is shunted across the inductance- 26.

To energize the output circuits 13 land 15 of the tubes there has been provided a frequency changer or oscillator 35. The particular form of oscillator which 4has been illustrated is a common form of vacuum tube oscillator comprising what is known as the Hartley circuit. This oscillator comprises a tube 36 having the usual grid or control element 37, plate 38 and electron-emission element or filament 39. The plate 38 is connected by a conductor 40 to the positive conductor of a source of direct current 41.y The negative conductor of kthis source is connected to one end 42 of the inductance 43, This i11- ductanee 43 has its other terminal connected to the grid 37 by means of conductor 44. The C-battery 45 may be inserted in this conductor 44 in order to place a negative potential upon the grid 37. The midpoint of the inductance 43 is connected by means of conductor 46 with the filament 39. Means are also preferably provided for controlling the frequency of this oscillator and for that purpose there has been provided a variable condenser 47 in shunt with the inductance 43. The plate circuit and the filament of this oscillator are preferably energized from a source 49 of alternating current. This source of alternating current which may be at some standard frequency, for example from 25 to 200 cycles, is preferably passed thru a. rectifier for converting the current to a unidirectional pulsating current. For this purpose it is preferable to employ the transforlner 50 having its primary coil connected to the source 49 and its secondary coil 51 connected to a rectifier. This rectifier preferably comprises two tubes or cells 52 which will pass current in one direction only. These cells 52 have their respective like elements connected to the terminals of the secondary coil 51 and their other elements connected together to a common conductor 53. This conductor 53 supplies the positive potential for the plate while the conductor 54 which is connected to the midpoint of the secondary coil 51 supplies the negative potential. Te energize the {ilament 39 of the oscillator tube there is preferably provided a secondary coil 55 which is connected te the terminals of the filament in series with the adjustable resistance 56. A potentiometer 57 is also shunted across the terminals of the filament 39 and has its contact arm connected to the conductor 46. The rectifier circuit 41 is preferably provided with a filtering device to smooth out ripples in the current. This filtering device, as shown.I comprises two choke coils 58 in series with the conductor 54. A condenser 59 is connected between the conductor 53 and the midpoint between the choke coils 58. i

Thus it will be seen that there has been provided an oscillator which is energized from a source of alternating current. The frequency of this oscillator may be controlled by means of the condenser 47 and is preferably sufciently high to be above audibility. In Figs. 1 and 2 of the drawing there are shown two different arrangements for coupling the oscillator to the tubes 10 and 11. In the arrangement shown in Fig. 1 the lower terminals of the inductances 25 and 29 are connected together and to the conductor 60 of the oscillator. The filaments of the two tubes 10 and 11 are preferably connected in parallel by means of the conductors 61 and 62 connected to the conductor 60 by means of a series impedance such as a variable condenser 64 having one of its terminals connected to the conductor 60 and its other terminal 65 connected to the conductor 62. This condenser G4 serves two different functions. It provides a high frequency impedance to control Athe current passing thru the filaments 18 and also serves as a further means for regulating the frequency of the oscillator 35 since it is connected in shunt to the inductance 43 in series with the filaments 18.

ylln operating the system as shown in' lfig. 1 the oscillator 35 is tuned by means of the variable condenser f7 to the desired frequency which preferably is above audibility. "lhe current output of the oscillator may be regulated in any well known manner such as by l varying the plate potential or by changing the brightness of the filament. 'lhe current passing thru the condenser' 64 and the filaments 18 may be controlled by varying the capacity of the condenser 64;. rlhe output circuits of the tubes 10 and 11 will be energized by a -periodically varying current butsince this current is at a frequency above audibility no audible hum will be apparent in the output circuit. rllhe frequency of the oscillator may be adjusted to be of radio-frequency. `When interrupted continuous amplitude radio frequency signaling waves are being received, as in telegraphic communication the voscillator frequency may be adjusted so as to beat with the incoming carrier frequency and this beat note may be of audible frequency. lt is also possible to so adjust the potential of the C- battery 24 that the tube 10 will function as a modulator and then the frequency of the oscillator may be adjusted to beatwith the incoming signals and this beat may then be amplified as in the super-heterodynesystems. This system is also applicable to what is known as the homodyne method of receiving carrier wave signals. lin receiving by this systemthe oscillator is tuned to, the same frequency as the carrier frequency of the incoming signals.

, llt is of course understood that in using this Ate system in radio receivingsets which are commonly used for radio telephone reception the frequency of the oscillator is always main tained above audibility so that no audible hum will interfere with the reception.

ln the modification shown in Fig. 2 there has been shown meansfor inductively coupling the oscillator to the tubes. lin this hgure the oscillator is of the 4same type as that illustrated in Fig. l, altho foi1 convenience it has been shown as being energized from batteries, battery supplying the plate 38 and battery 66 supplying the current for the filament 39 of the tube 36. In this oscillator the inductance has been shown as separated into two portions 67 and 68 which are respectively inductively coupled with secondary inductances 69 and 70. One terminal of the'inductance 69 is connected to the lower terminal of the inductance 25 while the other terminal of the inductance 69 is connected to the filament 18 by means of conduc tor 71. correspondingly one terminal of the inductance 70 is connected to the lower terminal of the inductance 29 While the other terminal of the inductance 70 is connected by conductor 72 with one terminal of a filament 18 of the tube 11. Variable condenser 73 is connected between the other terminal of the filament 18 of the tube 11 and the lower terminal of the inductance 25. Also variable condenser 74 is inserted between the other terminal ofthe filament 18 of the tube l1, and the lower terminal of the inductance 29. rllhe operation of this system is essentially the same as vthe operation of the system shown in l41 ig. 1. However, the inductive coupling of the oscillator with the tubes provides better control of the current.

l claim:

l. ln a system for repeating signal energy. an electron relay having input and output; circuits, means for coupling the input circuit to a source of signal energy of carrier frequency, and means for energizing theoutput circuit with pulsating current of carrier frequency, the frequency of said energizing circuit serving to react with the repeated signal energy thereby effecting current variations in the output circuitI which differ both from the signal energy and the energizing current.

2. ln a system for repeating signal energy, an electron relay having a iilamentary cathode, an anode, and a control electrode, an input circuit connected lacross the control electrode and the cathode, an output circuit con nected across the anode and cathode, means for couplingysaid input circuit with a source of signal energy of radio frequency, and means for effecting energization of the cathode by pulsatin current of a frequency above audibility, the frequency of the cathode energizing current serving to react with the signal energy whereby current variations in the output circuit dider both from the signal energy and said energizing current.

l3. lln a signal receiving system, an electron relay having input and output circuits, means for coupling the input circuit to a source of signal energy of radio frequency, signal translating means associated with the output circuit, and means for energizing the output circuit with a pulsating current of radio frequency, the frequency of said A'energizing current reacting with the signal energy whereby the frequency of the energizing current determines the character of the translator response. A t

4. In a signal receiving system, anelectron relay having a filamentary cathode and input and output circuits, means for 'coupling the input circuit to a source of signal energy of radio frequency, means for energizing said Stil lim

cathode with a local source of pulsating current of a frequency above audlbility, and translator means associated with the output circuit, the frequency of the energizing current serving toreact with the frequency of signal energyl thereby effecting resultant vari ations in the output circuit which differ' in frequency from the frequency of either said signal energy or said energizing current. m 5. In a signal receiving system, an electron relay having a filamentary cathode and input and output circuits, means for coupling the input circuit to a source of signal energy of radio frequency, means for energizing 15 both said cathode and said output circuit with pulsating current of a frequency above audibility, and means for translating the resultant current variations in the ouptut circuits, said resultant variations being produced 2o by the reaction between the frequency of the energizing currents and that of the signal energy.

6. In a radio receiving system, an electron relay having input and output circuits, means for coupling the input circuit to a source of signal energy of radio frequency, an oscillator for supplying energizing current to the output circuit, the frequency of the oscillator being above audibility and adapted to beat 3\ With the radio signal frequency which is repeated in the output circuit. e e 7. In an electron relay system, an electron relay having input and output circuits, means for causing current variations of radio frequency in said input circuit whereby corresponding amplified variations are effected in said output circuit, and means for energizing the output circuit with pulsating current of super-audible frequency differing from 4o said first mentionedradio frequency, the frequency of said energizing current variations serving together With said first mentioned variations to effect current variations in the output circuit of a frequency component 4.3 differing both from said radio and said superaudible frequencies.

8. In an electron relay system, an electron relay having a filamentary cathode, an anode, and a control electrode, control and output 5o circuits associated with said relay, means for causing current variations of radio frequency in said input circuit whereby corresponding variations are caused in the output circuit, and means for effecting energiza- :.5 tion of the cathode by pulsating currentv of super-audible frequency differing from said radio frequency, said combined frequencies serving to cause current variations in the output circuit of a frequency component differ- 60 ing from said radio and super-audible frequencies.

In testimony whereof, I have hereunto set niy hand.

FREDERICK A. KOLSTER. 

